Tension leg platforms (TLP), which are semi-submersible marine structures, have been widely used recently in order to perform drilling or production in submarine oil or gas fields.
The conventional TLP is constituted with a hull, which is structured with pontoons and columns, and tendons for supporting the hull in the seabed.
As the drilling or production works are performed through a riser, which is extended from the hull to the seabed, it is imperative that the motion of the hull be minimized in order to provide stable working conditions.
Meanwhile, external disturbances such as tidal currents or waves affect the hull of the semi-submersible marine structure floating on the sea, causing the hull to move in the lateral direction. If the hull moves excessively in the lateral direction, it becomes difficult to perform the work because, for example, the riser is damaged.
There have been efforts recently for developing technologies for minimizing or readily controlling the motion cause by external disturbances.